The present invention relates generally to fuel injector control circuits.
Known fuel injector control circuits generally comprise an open coil and a close coil for each fuel injector. To inject fuel into the cylinder, it is necessary to activate the open coil and then the close coil. Some applications require that the close coil on a given cylinder be activated before the associated open coil is deactivated. This is known as simultaneous excitation.
Known fuel injector fuel circuits connect each coil to the power supply with a different switch (such as a FET or other gate). Thus, for an 8 cylinder engine, 16 high side gates were required, each with associated drive circuitry.
When a coil is energized, some energy is stored in a magnetic field that surrounds the coil. When the coil is de-energized, it is desirable to recover some of the energy that was stored in the magnetic field. This energy recovered is done by a known technique called xe2x80x9crecirculation.xe2x80x9d
The present invention provides cost saving by reducing the number of high side gates and the associated drive circuitry from 16 to as few as 4 (for an eight cylinder engine). Various configurations are illustrated herein, with different benefits and features in each. However, as a general principal, each of these utilizes high and low side gates which selectively activate selected coils via a matrix.